David Cameron has claimed Ed Miliband switched his energy supplier despite questioning the point of consumers shopping around, as the two clashed again on fuel bills in the Commons.

The prime minister said the Labour leader had followed his advice to look for a better deal despite attacking him before for urging others to switch.

Mr Miliband said the only way to cut bills was "to switch prime ministers".

He called for an immediate price freeze - but Mr Cameron said this was a "con".

The party leaders clashed for the fourth time in a row about energy prices at Prime Minister's Questions.

'One-trick pony'

The Labour leader said the government's promise of a competition review reporting next year was inadequate, saying it would kick the issue "into the long grass" when consumers needed help straightaway.

Mr Cameron said he wanted the competition review to start straightaway and pointed out Labour peers in the House of Lords had backed calls for a decarbonisation target that would actually force up household bills.

Once an investigation is launched - and I am told that the prime minister is very close to initiating one - a cloud of expensive uncertainty will descend on the industry

He said Mr Miliband had switched his own supplier despite attacking the lack of competition in the market, and that his new provider - which he did not name - opposed the Labour leader's call for a 20-month price freeze.

"You switched your supplier. Yes. You went to one of these insurgent companies to cut your bills. Isn't it typical? You come here every week and attack Tory policy, and you go home and adopt Tory policy to help your own family."

Accusing Mr Miliband of being a "one-trick pony", Mr Cameron said greater switching was part of the more competitive market that he wanted and Labour's policy would result in "less choice, less competition and higher prices".

The Department of Energy and Climate Change has said more than 21,000 people have saved an average of £131 on their energy bills through collective switching, in which households club together to change supplier.

'PR man'

But Mr Miliband said the prime minister was a "PR man" for the energy industry and his rhetoric on consumer protection had gone "from Rambo to Bambi in four short years".

We will go on at the big six until they persuade the public they are being open and transparentNick Clegg, Deputy Prime Minister

"You're so on the side of energy companies, we should call them the big seven - the prime minister and the big six energy companies."

Mr Cameron said the Labour leader had nothing to say about the economic recovery, calling on him to apologise for past claims that the UK was facing a "lost decade" of growth and that new private sector jobs would not replace those being cut in the public sector.

He also accused Mr Miliband of "weakness" over the proposed high-speed rail line, saying that uncertainty in Labour ranks about whether to support the multibillion-pound infrastructure project was a "pathetic spectacle".

Labour has said it still supports the project but could cancel it if costs cannot be brought under control.

'Price alibi'

Meanwhile, the head of one of the UK's biggest energy companies has suggested that smaller providers have an unfair cost advantage.

Tony Cocker, the chief executive of E.On, said small companies were excused from paying some of the environmental and social levies.

Such levies make up between 8% and 9% of the average bill.

Mr Cocker told BBC Radio 4's Today programme: "The small companies are exempt from a number of environmental and social obligations. Not all, but some of them."

But Deputy Prime Minister Nick Clegg said some firms were using green levies as an "alibi" for price increases, saying it was "implausible" to blame them for double-digit prices rises being seen.

"We will go on at the big six until they persuade the public they are being open and transparent about how they arrive at these mind-numbing bill increases," he said.

'Naive'

Asked at his monthly press conference about the planned review of green and social charges, he said he would approach it pragmatically but would not "turn his back" on the environment or cut assistance for tackling fuel poverty.

"I don't want to throw the poorest in the land to the wolves through any hasty or ill-thought out change," he said.

He also attacked Mr Miliband's proposed price freeze, suggesting the "only green thing about this policy con is its naivety".

Comparing the pledge with the Lib Dems' pre-2010 promise to oppose a rise in student tuition fees - which Mr Clegg had to apologise for not keeping - he predicted the opposition leader would be left with "egg on his face".